Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/14—Polysiloxanes containing silicon bound to oxygen-containing groups
  • C08G77/18—Polysiloxanes containing silicon bound to oxygen-containing groups to alkoxy or aryloxy groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
  • C08G77/22—Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen
  • C08G77/28—Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen sulfur-containing groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes
  • C08L83/08—Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
  • C09D183/04—Polysiloxanes
  • C09D183/08—Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen, and oxygen
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J183/00—Adhesives based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Adhesives based on derivatives of such polymers
  • C09J183/04—Polysiloxanes
  • C09J183/08—Polysiloxanes containing silicon bound to organic groups containing atoms other than carbon, hydrogen, and oxygen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
  • C08L2205/025—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend
  • C08L2205/035—Polymer mixtures characterised by other features containing three or more polymers in a blend containing four or more polymers in a blend

Definitions

• the present invention relates to dual curing silicone compositions which are capable of cross-linking when subjected to radiation in the ultraviolet (“UV”) region of the electromagnetic spectrum and by a moisture condensation method and applications using such compositions.
• UV ultraviolet
• Silicone rubber and liquid compositions exist in various forms and their characteristics may be modified to impart specific characteristics such as cure chemistry, viscosity, polymer type and purity. They can be formulated into one-part or two-part systems and a particular silicone composition can be engineered to be cured by more than one mechanism. Moisture-curing mechanisms, heat-curing mechanisms, and photoinitiated curing mechanisms are among those mechanisms used to initiate cure, i.e., cross-linking of reactive silicones. These mechanisms are based on either condensation reactions, whereby moisture hydrolyzes certain groups on the silicone backbone, or addition reactions which can be initiated by a form of energy, such as electromagnetic radiation or heat.
• reactive organopolysiloxanes can be cured by heat in the presence of a peroxide, or they can be cured by heat in the presence of a silicon hydride-containing (SiH) compound and a metallic hydrosilylation catalyst, such as an organo-platinum catalyst.
• SiH silicon hydride-containing
• metallic hydrosilylation catalyst such as an organo-platinum catalyst.
• moisture curable materials are manufactured by endcapping ⁇ , ⁇ -silanol terminated silicones with various crosslinkers such as alkoxysilanes, oximinosilanes, acetoxysilanes, aminosilanes, and other silanes with hydrolyzable groups attached to the silicon atom(s) thereof.
• crosslinkers such as alkoxysilanes, oximinosilanes, acetoxysilanes, aminosilanes, and other silanes with hydrolyzable groups attached to the silicon atom(s) thereof.
• the resulting silicone materials are stored in moisture impermeable containers.
• the materials are extruded or otherwise applied and exposed to ambient conditions for curing.
• the moisture in the air then will hydrolyze the hydrolyzable groups (such as alkoxy, oximino, acetoxy, and amino) on the silicon atom(s) to form silanol, either with or without inclusion of a catalyst.
• the resulting silanol can then further react with remaining unhydrolyzed groups in a condensation reaction, to form a siloxane linkage resulting in the cure of the silicone material.
• a third curing mode ultraviolet light curing
• the curing is relatively fast, with the cured elastomer showing better adhesion to the substrates.
• a secondary cure mode usually moisture cure can be further incorporated.
• UV cure of silicone compositions can be achieved by either a thiol-ene cure or by an acrylate cure.
• a thiol functional silicone is reacted with an alkenyl functional silicone. The cure is fast and the surface dry to the touch upon the completion of the cure.
• the cured product does not heat age well, and the uncured composition tends to have poor adhesion, lack long-term storage stability, and have objectionable odor.
• acrylate functional silicone is usually storage stable and the cured products exhibit excellent high temperature resistance up to temperatures of 125° C.
• the surface cure tends to be incomplete and the cured product often times tends to be tacky and brown in color.
• the present invention provides compositions which cure through a dual-curing mechanism.
• a dual cure organopolysiloxane composition comprising a first organopolysiloxane having at least two mercapto functional groups; and a second organopolysiloxane have alkenyl groups and trialkoxysilyl groups.
• an organopolysiloxane having at least two mercaptoalkyl functional groups in polymer is provided.
• the first organpolyosiloxane may or may not have terminal mercapto groups.
• Preferably the first organpolyosiloxane does not comprise terminal mercapto groups.
• the first organopolysiloxane comprises at least one unit of the formula:
• Ra represents a divalent hydrocarbon group
• Rb represents alkyl, aryl, H, hydroxyl or alkoxy containing group
• c is 0, 1 or 2.
• the preferred SH content in this organopolysiloxane is 0.5-35 weight percent.
• Ra is a divalent hydrocarbon group with 1-8 carbons
• Rb is a C 1-8 alkyl group or phenyl moiety or alkoxy moiety.
• the first organopolysiloxane is generally present in the dual cure silicone composition in an amount from 1 to 90 weight percent.
• an organpolyosiloxane having both alkenyl groups and trialkoxysilyl groups is provided as a second element of the composition of the present invention.
• the second organopolysiloxane is made as a product of alkenyl-functionalized polysiloxanes and a stoichiometric less amount of trialkoxysilyl functionalized silane in the presence of hydrosilation catalyst.
• Such compositions are generally present in the dual cure silicone composition in an amount from 2 to 90 weight percent.
• the resultant organopolysiloxane composition of the present invention is a dual-cure composition. As such the composition is subject to two curing mechanisms.
• the dual-cure organopolysiloxane may be UV cured, moisture cured, or a combination of the two cure techniques.
• the UV cure mechanism in this formulation is suitably free-radical cure.
• the photoinitiators useful in the present invention may be selected from any known free radical type photoinitiator effective for promoting crosslinking reactions.
• suitable photoinitiators include UV initiators such as benzophenone and substituted benzophenones, acetophenone and substituted acetophenones, benzoin and its alkylesters, xanthone and substituted xanthones.
• Desirable photoinitiators include diethoxyacetophenone (DEAP), benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, diethoxyxanthone, chloro-thioxanthone, azo-bisisobutyronitrile, N-methyl diethanolaminebenzophenone, and combinations thereof.
• the selection of photo initiator depends on the application thickness, UV wavelength, cure speed, and compatibility with formulation etc. For UV wavelength lower than 350 nm, alpha hydroxyketone type may suitably be employed.
• the photoinitiator may be present in any effective amount, desirable ranges include about 0.1 to about 5% by weight, such as about 0.2 to about 1% by weight.
• compositions may also include moisture curing catalysts to enhance the rate at which the hydrolyzable groups on the organopolysiloxane react with moisture to cure.
• the moisture curing catalysts include organo-metal catalysts including titanates such as tetraisopropylorthotitanate and tetrabutoxyorthotitanate, as well as metal carboxylates such as dibutyltin dilaurate, dibutyltin dioctoate and the like.
• a particularly suitable moisture curing catalyst is diisopropoxytitanium bis(ethylacetoacetate).
• the moisture cure catalyst should be used in an amount sufficient to effectuate moisture cure, which desirably is in the range of about 0.1 to about 5% by weight.
• Useful UV radiation sources include conventional mercury-vapor lamps designed to emit ultraviolet energy in various ultraviolet wavelength bands, LED curing lamp etc.
• useful radiation wavelength ranges include 200 to 400 nm.
• inventive compositions may also contain other additives so long as they do not interfere with the curing mechanisms.
• additives such as fillers, adhesion promoters, resins, pigments, moisture scavengers, fluorescent dye, inhibitors and the like may be included.
• Fillers such as fumed silica or quartz are contemplated. Fillers may be present in amounts up to about 30% by weight, such as about 4 to about 20% by weight.
• Inhibitors may be present up to about 5% by weight, desirably about 0.001 to about 1% by weight. The particular amount of inhibitor should be balanced in a given composition to produce or improve stability of the composition.
• Adhesion promoters may be present in amounts of up to about 5%, such as about 0.5% by weight.
• UV cure is generally effected in the range of 40 milliwatts/cm 2 (“mW/cm 2 ”) to about 300 mW/cm 2 , such as in the range of about 70 mW/cm 2 to about 300 mW/cm 2 .
• compositions of the present invention may be prepared by mixing together the respective components to obtain a substantially homogenous or uniformly blended material and stored in containers which are non-transmissive to UV light and moisture.
• a single package system is employed, but two-part package systems may be used if desired. Whereas single package products are ready-for-use upon being dispersed, two-part systems require mixing of the dispersed parts prior to use.
• compositions may be used as noted above in potting applications and coatings, encapsulations, gels for a variety of substrates including electronic parts and other heat-sensitive materials.
• mercapto containing siloxane (8 g, 3.5 wt % SH), dimethylvinylated silicone resin (10 g, 0.42 wt % vinyl content), vinyl terminated polydimethylsiloxane (10 g, 0.45 wt % vinyl content), dual cure siloxane A (4 g, 0.6 wt % vinyl content) and methyltrimethoxy silane (0.2 g) were added.
• the composition was mixed at 2000 rpm for 60 seconds; followed by the addition of photoinitiator 2-hydroxyl-2-methyl-l-phenyl-1-propanone (0.3 g), and butylated hydroxytoluene (0.06 g). The mixture was then mixed at 2000 rpm for 30 s. Diisopropoxytitanium bis(Ethylacetoacetate) (0.3 g) was then added. The final formulation was mixed under 2000 rpm for 60 s.
• Example A Similar as Example A, except that 10 g of dual cure siloxane A and 0.5 g methyltrimethoxy silane were added in the formulation.
• Example A Similar as Example A, except that 20 g of dual cure siloxane A and 1 g methyltrimethoxy silane were added in the formulation.
• mercaptopropyl and dimethoxysilyl terminated polydimethylsiloxane (4 g, 1.5 wt % SH), mercapto containing siloxane (5.3 g, 3.5 wt % SH), dimethylvinylated silicone resin (10 g, 0.42 wt % vinyl content), vinyl terminated polydimethylsiloxane (10 g, 0.45 wt % vinyl content) were added.
• the mixture was mixed at 2000 rpm for 60 seconds; followed by the addition of photoinitiator 2-hydroxyl-2-methyl-l-phenyl-1-propanone (0.3 g), and inhibitor butylated hydroxytoluene (0.06 g).
• the mixture was mixed at 2000 rpm for 30 s.
• Diisopropoxytitanium bis(Ethylacetoacetate) (0.3 g) was then added.
• the final formulation was mixed under 2000 rpm for 60 s

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• 2018
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